For FY 2017-18 : Due Date of FORM GSTR-9 was 31st January 2020 which was further extended to 05th February, 07th February and 09th February 2020 according to State wise.
For FY 2018-19 : Due Date of filing FORM GSTR-9 and FORM GSTR-9C has been extended to "31st October 2020 ( 31.10.2020 )" vide Notification No. 69/2020 - Central Tax, dated 30th September 2020.
No Penalty or Late Fees will be levied for filing FORM GSTR-9 and FORM GSTR-9C for FY 2018-19 since the Government has extended the due date to 31st October 2020. So no worry...